1. Field of the Invention
The present invention relates to a self-expanding bifurcated stent and apparatus and methods for inserting the same into a bifurcated anatomical structure.
2. Description of the Related Art
Numerous studies have reported the use of metallic stents for the treatment of stenotic lesions occurring in tubular anatomic structures (Wallace et al., 1986; Palmaz, 1988; Milroy et al., 1989; Gxc3xcinther et al., 1989; Riving et al., 1989). Placement of these stents is less invasive than surgical procedures and the stents provide more luminal space than most solid tube devices. Therefore, metallic stents have been widely used for treatment of stenotic diseases in humans. Several different types of stents have been used to treat both straight and curved lesions (Gillams et al, 1990).
The use of straight, cylindrical stents has some limitations. One major limitation is the treatment of lesions occurring at a bifurcation (Nashef et al, 1992). Many methods for stenting these lesions with straight stents have been described including side-by-side insertion (Morita, 1997), pull-through technique (Morita, 1987), creation of a T-configuration (Morita, 1987), Y-stenting (Fort, 1996), and V-stent insertion (Schampaert, 1996). However, no ideal method has been established because only straight stents with a cylindrical configuration are commercially available.
Additionally, the use of such a stent to treat disease at or near a branch of a bifurcation of a blood vessel runs the risk of compromising the degree of patency of the primary vessel and/or its branches of the bifurcation. This may occur as a result of several problems such as displacing diseased tissues, vessel spasm, dissection with or without intimal flaps, thrombosis, and embolism. For example, a bifurcated vascular or non-vascular lesion can be bridged by two straight cylindrical stents arranged in a Y-shape. One of the stents is longer forming one leg and the common trunk of the Y, while another short stent is attached to the longer one in an end-to-side fashion to form the other leg of the Y-shape. In this situation, the patency of the shorter leg is threatened by the fact that at the site of the attachment of the two stents the stent mesh of the longer stent interferes with the free flow of blood, bile, etc. Such an attachment has a high propensity for thrombosis and consequent occlusion in the vasculature, stenosis, bile congestion, inflammation, and eventually occlusion in the biliary tree. In the tracheobronchial system, mucus deposition will readily result in serious coughing, infection, and exclusion of the affected part of the lung from gas-exchange.
In one respect, the invention is a device suitable for implantation into an anatomical structure that includes, but is not limited to, a first plurality of wires that define a first leg, which has a first distal portion; a second plurality of wires that define a second leg, which has a second distal portion; and a common body that has a distal end and a proximal portion. The common body is formed from at least the first and second pluralities of wires. The proximal portion of the common body is adjacent to the distal portions of both legs, and both ends of at least one wire from one of the pluralities is located proximate (near) the distal end of the common body.
The wires in the first and second pluralities may be made from nitinol. The wires in the first and second pluralities may be made from FePt, FePd or FeNiCoTi. The wires in the first and second pluralities may also be made from FeNiC, FeMnSi or FeMnSiCrNi. The wires in the first and second pluralities may each have a diameter ranging in size from about 0.006 inches to about 0.014 inches. The first plurality of wires may include at least 6 wires. Both the legs and the common body may have tubular shapes with substantially uniform diameters. At least one of the legs of the device may be hand woven. At least one of the legs of the device may be machine woven. The device may also include a graft material attached to at least the common body. The graft material may be made from woven Dacron. The graft material may be made from polyurethane. The graft material may also be made from PTFE.
In another respect, the invention is a stent that includes, but is not limited to, a first plurality of flexible tubular strands woven to form a first leg that has a first distal portion. The flexible tubular strands in the first plurality cross each other to form a first plurality of angles. At least one of the angles in the first plurality of angles is obtuse. The stent also includes, but is not limited to, a second plurality of flexible tubular strands woven to form a second leg that has a second distal portion. The flexible tubular strands in the second plurality cross each other to form a second plurality of angles. At least one of the angles in the second plurality of angles is obtuse. The stent also includes, but is not limited to, a common body that has a common portion. The common body is formed from at least the first and second pluralities of flexible tubular strands. The common portion of the common body is adjacent to the distal portions of the first and second legs.
The flexible tubular strands in the first and second pluralities may be made from nitinol or biodegradable filaments.
In another respect, the invention is a stent that includes, but is not limited to, a first plurality of wires that define a first leg, which has a first distal portion. The stent also includes, but is not limited to, a second plurality of wires that define a second leg, which has a second distal portion. The stent also includes, but is not limited to, a third plurality of wires that define a third leg, which has a third distal portion. The stent also includes, but is not limited to, a common body that has a proximal portion and a distal end. The common body is formed from at least the first, second and third pluralities of wires. The proximal portion of the common body is adjacent to the distal portions of each of the three legs.
The wires in each of the pluralities may be made from nitinol. The first plurality of wires may include at least 5 wires. Each of the legs and the common body may have tubular shapes with substantially uniform diameters. At least one of the legs may be hand woven or machine woven. The stent may also include a graft material that is attached to at least the common body. The graft material may be made from woven Dacron. The graft material may be made from polyurethane.
In another respect, the invention is a stent that includes, but is not limited to, a first leg that has a first axis and a first end. The first leg includes, but is not limited to, a first wire that has a first segment and a second segment, which are separated by a bend in the first wire located proximate (near) the first end of the first leg. The first segment extends helically in a first direction around the first axis away from the first end of the first leg, and the second segment extends helically in a second direction around the first axis away from the first end of the first leg. The segments cross each other in a first plurality of locations. The stent also includes, but is not limited to, a second leg that has a second axis and a second end. The second leg includes, but is not limited to, a second wire that has a first segment and a second segment, which are separated by a bend in the second wire located proximate (near) the second end of the second leg. The first segment extends helically in a first direction around the second axis away from the second end of the second leg, and the second segment extends helically in a second direction around the second axis away from the second end of the second leg. The segments cross each other in a second plurality of locations. The stent also includes, but is not limited to, a common body that is formed from at least one end of each of the wires.
The first segment of the first wire may be positioned farther from the first axis than the second segment of the first wire at least one location among the first plurality of locations. The first segment of the first wire may be positioned farther from the first axis than the second segment of the first wire at each location of the first plurality of locations. The first and second wires may be made from nitinol.
In another respect, the invention is a method of creating a device suitable for implantation into an anatomical structure. The device may have a first leg, a second leg, and a common body. Each leg may have an end and a distal portion. The common body may have a proximal portion and a distal end. The method includes, but is not limited to, bending the wires in a first plurality of wires to create first bent portions in the wires. The first bent portions are arranged to define the end of the first leg. Each wire in the first plurality has two ends. The method also includes, but is not limited to, bending the wires in a second plurality of wires to create second bent portions in the wires. The second bent portions are arranged to define the end of the second leg. Each wire in the second plurality has two ends. The method also includes, but is not limited to, weaving the ends of the wires in the first plurality to create the first leg; weaving the ends of the wires in the second plurality to create the second leg; and weaving the ends of the wires in both pluralities to create the common body and the device. The proximal portion of the common body is adjacent to the distal portions of both legs.
The first bent portions may be bends or loops. The wires in the first and second pluralities may be made from nitinol. The wires in the first and second pluralities may each have a diameter ranging in size from about 0.006 inches to about 0.014 inches. The step of weaving the ends of the wires in the first plurality may be performed by hand or by machine.
In another respect, the invention is a method of creating a stent, which may have a first leg, a second leg, and a common body. Each leg may have an end and a distal portion, and the common body may have a proximal portion and a distal end. The method includes, but is not limited to, providing a weaving system that includes, but is not limited to, a first template that has first template projections, a proximal end and a distal end. The method also includes, but is not limited to, bending the wires in a first plurality of wires around the first template projections to create first bent portions in the wires. The first bent portions are arranged to define the end of the first leg. Each wire in the first plurality has two ends. The method also includes, but is not limited to, bending the wires in a second plurality of wires to create second bent portions in the wires. The second bent portions are arranged to define the end of the second leg. Each wire in the second plurality has two ends. The method also includes, but is not limited to, weaving the ends of the wires in the first plurality to create the first leg; weaving the ends of the wires in the second plurality to create the second leg; and weaving the ends of the wires in both pluralities to create the common body and the stent. The proximal portion of the common body is adjacent to the distal portions of both legs.
The weaving system may also include, but is not limited to, a second template that has second template projections, a proximal end and a distal end; and a third template that a proximal end and a distal end. The distal ends of the first and second templates may be configured to be placed within the proximal end of the third template. The step of bending the wires in the second plurality of wires may include bending the wires in the second plurality of wires around the second template projections to create second bent portions in the wires. The step of weaving the ends of the wires in both pluralities may include weaving the ends of the wires in both pluralities around the third template to create the common body and the stent.
The weaving system may also include, but is not limited to, a second template having a proximal end, a distal end, second template projections arranged around the second template proximate (near) the proximal end thereof, and an opening positioned between the proximal and distal ends of the second template. The opening is configured to accept the distal end of the first template. The step of bending the wires in the second plurality of wires may include bending the wires in the second plurality of wires around the second template projections to create second bent portions in the wires. The step of weaving the ends of the wires in the second plurality may include weaving the ends of the wires in the second plurality around the portion of the second template located proximally of the opening therein to create the second leg. The step of weaving the ends of the wires in both pluralities may include weaving the ends of the wires in both pluralities around the portion of the second template located distally of the opening therein to create the common body and the stent.
The first template projections may be pins, which may be attached to a ring engaged with the first template. The method may also include, but is not limited to, securing the wires in the first plurality of wires to the first template. The method may also include, but is not limited to, forming closed structures with the ends of the wires in both pluralities. The closed structures may be arranged to define the distal end of the common body. The method may also include, but is not limited to, heating the stent and the first template.